This invention relates generally to xerographic copying apparatus and, more particularly, to a contact fusing system for fixing electroscopic toner material to a support member.
In the process of xerography, a light image of an original to be copied is typically recorded in the form of a latent electrostatic image upon a photosensitive member with subsequent rendering of the latent image visible by the application of electroscopic marking particles, commonly referred to as toner. The visual image can be either fixed directly upon the photosensitive member or transferred from the member to a sheet of plain paper with subsequent affixing of the image thereto.
In order to permanently affix or fuse electroscopic toner material onto a support member by heat, it is necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This action causes the toner to be absorbed to some extent into the fibers of the support member which, in many instances, constitutes plain paper. Thereafter, as the toner material cools, solidification of the toner material occurs causing the toner material to be firmly bonded to the support member. In both the xerographic as well as the electrographic recording arts, the use of thermal energy for fixing toner images onto a support member is old and well known.
One approach to thermal fusing of electroscopic toner images onto a support has been to pass the support with the toner images thereon between a pair of opposed roller members, at least one of which is internally heated. During operation of a fusing system of this type, the support member to which the toner images are electrostatically adhered is moved through the nip formed between the rolls with the toner image contacting the fuser roll to thereby effect heating of the toner images within the nip.
Heretofore, prior art fusers of the type described have been constructed so that the roll members can be moved out of contact with each other during periods of non-use of the copier apparatus, otherwise flat areas may be formed on one or both of the fuser members. Those skilled in this area of technology will appreciate the complexity and the expense of the mechanism for effecting such disengagement with the subsequent engagement of the roll members. The desirability of eliminating such mechanisms will also be appreciated by those skilled in this art.
Accordingly, the principal object of this invention is to provide a new and improved electrostatic copying apparatus.
Another object of this invention is to provide a new and improved contact fusing apparatus for use in fixing toner images to copy sheets.
Still another object of this invention is to provide a contact fuser for fixing toner images which comprises a pair of permanently nipped fuser roll members operatively coupled to the main drive of a copier apparatus via a one-way clutch.
Yet another object of this invention is to provide a contact fuser which is capable of fusing toner images notwithstanding the occurrence of a paper jam.